The present invention relates to a collector circuit applicable to fluid circulation systems comprised in drilling rigs. A further aspect of the present invention relates to a process for continuous circulation of a fluid flow towards the bottom of a drilling well for a drilling rig, wherein said fluid flow, e.g. drilling mud, runs in a fluid circulation system comprising a collector circuit according to the present invention.
In particular, the present invention relates to the conformation of the collector circuit applicable to a circulation system, even an already existing one, for continuous circulation of drilling fluids during all of the operating sequences of a drilling rig. Furthermore, the present invention relates to the steps of the process for continuous circulation of a fluid flow in a circulation system according to the present invention during all of the operating sequences of a drilling rig.
The circulation system according to the present invention comprises at least one collector circuit allowing continuous circulation of fluids, such as, for example, drilling mud, during all of the operating steps of a drilling rig. Said collector circuit can at least intercept and divert at least a part of the fluid flow circulating in the fluid circulation system according to the present invention.
The collector circuit, the system and the associated process are aimed at improving the safety of drilling rigs, by automatizing operations that are normally carried out manually in traditional drilling rigs.
It is known to those skilled in the art that in a drilling rig fluids such as drilling mud need to circulate through a drill bit located at the bottom of the drilling well or in proximity thereto. Said drill bit is located at the end of a series of drilling elements, such as drill pipes. In particular, it is necessary that fluid circulation towards the drill bit also takes place during the steps of inserting or removing the drill pipes, in order to prevent damage to the open hole of the drilling well. In prior-art systems, pressure fluctuations at the bottom of the drilling well occur when turning on or off the drilling pump of the circulation system while inserting or removing pipes. Such pressure fluctuations may cause landslips and/or entry of fluids into the well.
This problem is particularly felt for critical wells, such as, for example, deep, deviated, horizontal and extended-reach wells.
For better performance and safety, in fact, the pressure at the bottom of the drilling well should be constantly kept at desired levels.
Collector devices for fluids such as drilling mud are known in the art as manifolds. The function of said collector devices is to intercept and divert a fluid flow, e.g. drilling mud coming from the drilling pumps, allowing both circulation via a main circuit leading to the top drive and lateral circulation via a secondary circuit. Lateral circulation normally occurs during the steps of adding or removing one or more drill pipes connected in series to define the drill length, as is known to those skilled in the art. Lateral circulation via said secondary circuit is normally activated by connecting a duct to a radial aperture provided on the drilling elements, such as connectors, subs or drill pipes.
Said radial aperture normally comprises safety valves. The connection between the radial aperture and the secondary circuit, which is fluid-dynamically connected to the collector circuit, can be established either manually or by means of automatic devices for opening such radial valves in a semiautomatic manner, during the steps of adding or removing drill pipes.
At least one portion of such collector devices cannot undergo maintenance when the device is inserted in the drilling mud circulation system and a fluid flow is running through it.
In addition, such collector devices do not ensure a high degree of operator safety, particularly in the portion of the collector circuit towards the secondary circuit. In the operating configuration for diverting the fluid flow towards the secondary circuit, in fact, such collector devices have just one valve for separating the fluid circulation circuit from the secondary circuit.
Furthermore, the collector devices currently available in the art are separate devices that cannot be interfaced to the drilling rig from a control viewpoint.
Prior-art collector devices do not allow performing a function for filtering the fluids flowing in the fluid circulation system.
It is known from US patent application 2004/178003 a drilling system for drilling a bore hole into a subterranean earth formation, wherein at least a portion of the mud flow from the primary mud pump is diverted to the mud discharge outlet, thereby creating a backpressure system to readily increase annular pressure.
US patent application 2013/133948 discloses a well drilling system which can include a hydraulics model which determines a modeled fluid friction pressure and a calibration factor applied to the modeled friction pressure, and a flow control device which is automatically controlled in response to a change in the calibration factor. A well drilling method can include drilling a wellbore, a fluid circulating through the wellbore during the drilling, determining a calibration factor which is applied to a modeled fluid friction pressure, and controlling the drilling based at least in part on a change in the calibration factor.
It is also known form US patent application 2007/227774 a method for controlling formation pressure during the drilling of a borehole through a subterranean formation includes selectively pumping a drilling fluid through a drill string extended into a borehole, out a drill bit at the bottom end of the drill string, and into an annular space between drill string and the borehole.
Patent application WO2011/050500 discloses a multi-level refined throttle manifold and an automatic control system. The multi-level refined throttle manifold system is composed of multiple plate valves and a throttle valve that are connected in parallel. The automatic control system enables micro-adjustment of wellhead return pressure under different pressure grades through starting and closing the different plate valves, and through adjusting the throttle valves continuously.
It is known from US 2012/227961 a method for determining annulus/wellbore fluid pressure, which is corrected for movement of a pipe string into or out of a wellbore, includes determining an initial annulus fluid pressure in the wellbore.